Stop installing pre-commit in dev

It's not necessary thanks to tox & pre-commit ci and it's kinda overbearing
towards people who already have it installed.

.github/CONTRIBUTING.md

@@ -81,20 +81,20 @@ $ make html
 
 The built documentation can then be found in `docs/_build/html/`.
 
-To avoid committing code that violates our style guide, we strongly advise you to install [*pre-commit*] [^dev] hooks:
+To avoid committing code that violates our style guide, we strongly advise you to install [*pre-commit*] and its hooks:
 
 ```console
 $ pre-commit install
 ```
 
-You can also run them anytime (as our *tox* does) using:
+This is not strictly necessary, because our [*tox*] file contains an environment that runs:
 
 ```console
 $ pre-commit run --all-files
 ```
 
-[^dev]: *pre-commit* should have been installed into your virtualenv automatically when you ran `pip install -e '.[dev]'` above.
-        If *pre-commit* is missing, your probably need to run `pip install -e '.[dev]'` again.
+and our CI has integration with `pre-commit.ci <https://pre-commit.ci>`_.
+But it's way more comfortable to run it locally and *git* catching avoidable errors.
 
 
 ## Code

setup.py

@@ -56,11 +56,11 @@
         "mypy>=0.971; python_implementation == 'CPython'",
         "pytest-mypy-plugins; python_implementation == 'CPython'",
     ],
-    "tests": {
+    "tests": [
         "attrs[tests-no-zope]",
         "zope.interface",
-    },
-    "dev": {"attrs[tests,docs]": ["pre-commit"]},
+    ],
+    "dev": ["attrs[tests,docs]"],
 }
 # Don't break Paul unnecessarily just yet. C.f. #685
 EXTRAS_REQUIRE["tests_no_zope"] = EXTRAS_REQUIRE["tests-no-zope"]

tox.ini

@@ -58,7 +58,6 @@ commands =
 
 
 [testenv:pre-commit]
-basepython = python3.10
 skip_install = true
 deps = pre-commit
 passenv = HOMEPATH  # needed on Windows